L O M 



[150 ] 



LOW 



fossil loligo are preserved, still distended, 

 as when they formed parts of the organi- 

 zation of living bodies, and retaining the 

 same juxta-position to an internal rudi- 

 mentary shell resembling a horny pen, 

 which the ink-bag of the existing loligo 

 bears to the pen within the body of that 

 animal. 



LO'MONITE. Diatomous Geolite. Named 

 after its discoverer, Gillet Laumont. For 

 a description of this mineral, see Lau- 

 monite. 



LONCHO'PTERIS MANTfi'LLI. A SpCClBS of 



fossil fern found in the shales and clays of 

 Tilgate Forest, and thus named after Dr. 

 Mantell. It is characterized, says Dr. 

 Mantell, by the distribution of the ner- 

 vures of the leaves. This fern probably 

 did not exceed a few feet in height. The 

 Lonchopteris Mantelli is very beautifully 

 figured in Dr. Mantell's Geology of the 

 South-East of England, and in his Won- 

 ders of Geology. 



LONDON BASIN. The deposits of the Lon- 

 don basin belong to the eocene period ; 

 they are aqueous. 



LONDON CLAY. This formation consists 

 of a bluish or blackish clay, lying imme- 

 diately over the plastic clay and sand, 

 and is an upper member of the arena- 

 ceous and argillaceous formation that 

 covers the chalk. Its thickness is very 

 considerable, sometimes exceeding 500 

 feet, but varying from one to five hundred 

 feet. It contains layers of ovate, or 

 flattish masses of argillaceous limestone. 

 These masses, called septaria, are some- 

 times continued through a thickness of 

 two hundred feet ; of these Parker's 

 cement is made. From the London clay 

 three or four hundred species of testacea 



i have been procured, but the only bones of 

 vertebrated animals are those of reptiles 

 and fish. Remains of turtles have been 

 dug out of this deposit at Highgate and 

 Islington, and some bones of a crocodile 

 were discovered by Mr. Parkinson ; nau- 

 tilites also are found in it. The shells of 

 the London clay mostly belong to genera 

 inhabiting onr present seas. The Lon- 

 don clay belongs to the eocene period. 



LONGICO'RNES. (from longusand corwM,Lat. 

 long-horned.) A family of insects in Cu- 

 vier's arrangement, and so named from the 

 length of their antennae, which are filiform 

 and cetaceous, and usually as long, often 

 longer, than the body of the insect. 



LONGIPE'NNES. (from longus and penna, 

 Lat. long wings.) A family of birds in 

 Cuvier's arrangement, including those 

 birds, which, from the great strength of 

 their wings, are to be met with in all lati- 

 tudes. They are recognised by the great 

 length of their wings, whence they de- 

 rive their name, and by their bill, which 



in some genera is hooked at the end, in 

 others simply pointed. 



LONGIRO'STRES. (from longus and ros- 

 trum, a beak, or bill, Lat.) A family of 

 birds comprising the waders, or birds with 

 long bills. 



LO'NGITUDE. (longitudo, Lat. longitude, 

 Fr. longitudine, It.) The distance of any 

 part of the earth to the east or west of 

 any place. The meridian passing through 

 the observatory at Greenwich is as- 

 sumed by the British as a fixed origin, 

 from whence terrestrial longitudes are 

 measured. And as each point on the 

 surface of the earth passes through 360, 

 or a complete circle, in twenty-four hours, 

 at the rate of 15 in an hour, time be- 

 comes a representative of angular motion. 

 Hence, if the eclipse of a satellite happens 

 at any place at eight o'clock in the even- 

 ing, and the nautical almanack shows that 

 the same phenomenon will take place at 

 Greenwich at nine, the place of observa- 

 tion will be 15 of west longitude. In 

 the case of stations differing only in lati- 

 tude, the same star comes to the meridian 

 at the same time, but at different altitudes. 

 In that of stations differing only in longi- 

 tude, it comes to the meridian at the 

 same altitude, but at different times. 

 Supposing, then, that an observer is in 

 possession of any means by which he can 

 certainly ascertain the time of a known 

 star's transit across his meridian, he 

 knows his longitude; or if he knows the 

 difference between its time of transit 

 across his meridian and across that of any 

 other station, he knows the difference of 

 longitudes between those two places. 



LONGITU'DINAL. (longitudinaire, Fr. lon- 

 gitudinale, It.) Pertaining to longitude 

 or length. 



In conchology, the length of the shell 

 from the apex to the base ; thus, longi- 

 tudinal strise, &c., are those which radiate 

 from the apex to the base. 



LOPHI'ODON. (from Xo<pig and oSovQ, Gr.) 

 A fossil genus of animals, now entirely 

 extinct, allied to the tapir, rhinoceros, 

 and hippopotamus, and connected with 

 the Anoplotherium and Palseotherium ; 

 so named from certain points, or emi- 

 nences, on the teeth. Fifteen species 

 have beeu discovered in the same fresh- 

 water formations as contain remains of 

 the palseotherium. 



LOWER CHALK. The chalk formation or 

 series is generally divided into six distinct 

 members, namely, the lower green-sand ; 

 the gault ; the upper green -sand ; the 

 chalk without flints, or the lower chalk ; 

 the chalk with flints, or the upper chalk, 

 and the Maestricht beds. This arrange- 

 ment is, however, altered by some writers, 

 inasmuch as a more minute subdivision 



